308 lines
7.8 KiB
C
Executable File
308 lines
7.8 KiB
C
Executable File
/*
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* cpu_rmap.c: CPU affinity reverse-map support
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* Copyright 2011 Solarflare Communications Inc.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published
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* by the Free Software Foundation, incorporated herein by reference.
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*/
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#include <linux/cpu_rmap.h>
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#include <linux/interrupt.h>
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#include <linux/export.h>
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/*
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* These functions maintain a mapping from CPUs to some ordered set of
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* objects with CPU affinities. This can be seen as a reverse-map of
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* CPU affinity. However, we do not assume that the object affinities
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* cover all CPUs in the system. For those CPUs not directly covered
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* by object affinities, we attempt to find a nearest object based on
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* CPU topology.
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*/
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/**
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* alloc_cpu_rmap - allocate CPU affinity reverse-map
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* @size: Number of objects to be mapped
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* @flags: Allocation flags e.g. %GFP_KERNEL
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*/
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struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags)
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{
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struct cpu_rmap *rmap;
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unsigned int cpu;
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size_t obj_offset;
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/* This is a silly number of objects, and we use u16 indices. */
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if (size > 0xffff)
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return NULL;
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/* Offset of object pointer array from base structure */
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obj_offset = ALIGN(offsetof(struct cpu_rmap, near[nr_cpu_ids]),
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sizeof(void *));
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rmap = kzalloc(obj_offset + size * sizeof(rmap->obj[0]), flags);
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if (!rmap)
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return NULL;
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kref_init(&rmap->refcount);
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rmap->obj = (void **)((char *)rmap + obj_offset);
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/* Initially assign CPUs to objects on a rota, since we have
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* no idea where the objects are. Use infinite distance, so
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* any object with known distance is preferable. Include the
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* CPUs that are not present/online, since we definitely want
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* any newly-hotplugged CPUs to have some object assigned.
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*/
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for_each_possible_cpu(cpu) {
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rmap->near[cpu].index = cpu % size;
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rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
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}
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rmap->size = size;
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return rmap;
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}
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EXPORT_SYMBOL(alloc_cpu_rmap);
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/**
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* cpu_rmap_release - internal reclaiming helper called from kref_put
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* @ref: kref to struct cpu_rmap
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*/
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static void cpu_rmap_release(struct kref *ref)
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{
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struct cpu_rmap *rmap = container_of(ref, struct cpu_rmap, refcount);
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kfree(rmap);
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}
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/**
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* cpu_rmap_get - internal helper to get new ref on a cpu_rmap
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* @rmap: reverse-map allocated with alloc_cpu_rmap()
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*/
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static inline void cpu_rmap_get(struct cpu_rmap *rmap)
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{
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kref_get(&rmap->refcount);
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}
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/**
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* cpu_rmap_put - release ref on a cpu_rmap
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* @rmap: reverse-map allocated with alloc_cpu_rmap()
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*/
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int cpu_rmap_put(struct cpu_rmap *rmap)
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{
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return kref_put(&rmap->refcount, cpu_rmap_release);
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}
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EXPORT_SYMBOL(cpu_rmap_put);
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/* Reevaluate nearest object for given CPU, comparing with the given
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* neighbours at the given distance.
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*/
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static bool cpu_rmap_copy_neigh(struct cpu_rmap *rmap, unsigned int cpu,
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const struct cpumask *mask, u16 dist)
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{
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int neigh;
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for_each_cpu(neigh, mask) {
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if (rmap->near[cpu].dist > dist &&
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rmap->near[neigh].dist <= dist) {
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rmap->near[cpu].index = rmap->near[neigh].index;
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rmap->near[cpu].dist = dist;
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return true;
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}
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}
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return false;
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}
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#ifdef DEBUG
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static void debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
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{
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unsigned index;
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unsigned int cpu;
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pr_info("cpu_rmap %p, %s:\n", rmap, prefix);
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for_each_possible_cpu(cpu) {
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index = rmap->near[cpu].index;
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pr_info("cpu %d -> obj %u (distance %u)\n",
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cpu, index, rmap->near[cpu].dist);
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}
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}
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#else
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static inline void
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debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
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{
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}
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#endif
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/**
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* cpu_rmap_add - add object to a rmap
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* @rmap: CPU rmap allocated with alloc_cpu_rmap()
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* @obj: Object to add to rmap
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*
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* Return index of object.
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*/
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int cpu_rmap_add(struct cpu_rmap *rmap, void *obj)
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{
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u16 index;
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BUG_ON(rmap->used >= rmap->size);
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index = rmap->used++;
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rmap->obj[index] = obj;
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return index;
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}
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EXPORT_SYMBOL(cpu_rmap_add);
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/**
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* cpu_rmap_update - update CPU rmap following a change of object affinity
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* @rmap: CPU rmap to update
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* @index: Index of object whose affinity changed
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* @affinity: New CPU affinity of object
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*/
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int cpu_rmap_update(struct cpu_rmap *rmap, u16 index,
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const struct cpumask *affinity)
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{
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cpumask_var_t update_mask;
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unsigned int cpu;
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if (unlikely(!zalloc_cpumask_var(&update_mask, GFP_KERNEL)))
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return -ENOMEM;
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/* Invalidate distance for all CPUs for which this used to be
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* the nearest object. Mark those CPUs for update.
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*/
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for_each_online_cpu(cpu) {
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if (rmap->near[cpu].index == index) {
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rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
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cpumask_set_cpu(cpu, update_mask);
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}
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}
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debug_print_rmap(rmap, "after invalidating old distances");
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/* Set distance to 0 for all CPUs in the new affinity mask.
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* Mark all CPUs within their NUMA nodes for update.
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*/
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for_each_cpu(cpu, affinity) {
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rmap->near[cpu].index = index;
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rmap->near[cpu].dist = 0;
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cpumask_or(update_mask, update_mask,
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cpumask_of_node(cpu_to_node(cpu)));
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}
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debug_print_rmap(rmap, "after updating neighbours");
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/* Update distances based on topology */
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for_each_cpu(cpu, update_mask) {
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if (cpu_rmap_copy_neigh(rmap, cpu,
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topology_thread_cpumask(cpu), 1))
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continue;
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if (cpu_rmap_copy_neigh(rmap, cpu,
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topology_core_cpumask(cpu), 2))
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continue;
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if (cpu_rmap_copy_neigh(rmap, cpu,
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cpumask_of_node(cpu_to_node(cpu)), 3))
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continue;
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/* We could continue into NUMA node distances, but for now
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* we give up.
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*/
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}
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debug_print_rmap(rmap, "after copying neighbours");
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free_cpumask_var(update_mask);
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return 0;
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}
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EXPORT_SYMBOL(cpu_rmap_update);
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/* Glue between IRQ affinity notifiers and CPU rmaps */
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struct irq_glue {
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struct irq_affinity_notify notify;
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struct cpu_rmap *rmap;
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u16 index;
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};
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/**
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* free_irq_cpu_rmap - free a CPU affinity reverse-map used for IRQs
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* @rmap: Reverse-map allocated with alloc_irq_cpu_map(), or %NULL
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*
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* Must be called in process context, before freeing the IRQs.
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*/
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void free_irq_cpu_rmap(struct cpu_rmap *rmap)
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{
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struct irq_glue *glue;
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u16 index;
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if (!rmap)
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return;
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for (index = 0; index < rmap->used; index++) {
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glue = rmap->obj[index];
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irq_set_affinity_notifier(glue->notify.irq, NULL);
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}
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cpu_rmap_put(rmap);
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}
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EXPORT_SYMBOL(free_irq_cpu_rmap);
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/**
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* irq_cpu_rmap_notify - callback for IRQ subsystem when IRQ affinity updated
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* @notify: struct irq_affinity_notify passed by irq/manage.c
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* @mask: cpu mask for new SMP affinity
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*
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* This is executed in workqueue context.
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*/
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static void
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irq_cpu_rmap_notify(struct irq_affinity_notify *notify, const cpumask_t *mask)
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{
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struct irq_glue *glue =
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container_of(notify, struct irq_glue, notify);
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int rc;
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rc = cpu_rmap_update(glue->rmap, glue->index, mask);
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if (rc)
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pr_warning("irq_cpu_rmap_notify: update failed: %d\n", rc);
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}
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/**
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* irq_cpu_rmap_release - reclaiming callback for IRQ subsystem
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* @ref: kref to struct irq_affinity_notify passed by irq/manage.c
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*/
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static void irq_cpu_rmap_release(struct kref *ref)
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{
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struct irq_glue *glue =
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container_of(ref, struct irq_glue, notify.kref);
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cpu_rmap_put(glue->rmap);
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kfree(glue);
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}
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/**
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* irq_cpu_rmap_add - add an IRQ to a CPU affinity reverse-map
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* @rmap: The reverse-map
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* @irq: The IRQ number
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*
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* This adds an IRQ affinity notifier that will update the reverse-map
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* automatically.
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*
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* Must be called in process context, after the IRQ is allocated but
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* before it is bound with request_irq().
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*/
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int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq)
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{
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struct irq_glue *glue = kzalloc(sizeof(*glue), GFP_KERNEL);
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int rc;
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if (!glue)
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return -ENOMEM;
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glue->notify.notify = irq_cpu_rmap_notify;
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glue->notify.release = irq_cpu_rmap_release;
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glue->rmap = rmap;
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cpu_rmap_get(rmap);
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glue->index = cpu_rmap_add(rmap, glue);
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rc = irq_set_affinity_notifier(irq, &glue->notify);
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if (rc) {
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cpu_rmap_put(glue->rmap);
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kfree(glue);
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}
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return rc;
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}
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EXPORT_SYMBOL(irq_cpu_rmap_add);
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